A method for treating liver dysfunction includes administering at least one member selected from a chitin oligosaccharide, a chitosan oligosaccharide and salts thereof, in an effective amount. As the chitin oligosaccharide, preferred is an oligosaccharide having a degree of polymerization of from 2 to 7. As the chitosan oligosaccharide, preferred is an oligosaccharide having a degree of polymerization of from 2 to 8. As the method for administration, it is preferred to add these oligosaccharides to foods, medicines or feeds, and to orally ingest them. However, when used as medicines, administration methods such as intravenous injection and muscular injection may be used.
